1. Field of the Invention
The present invention relates generally to speech and audio signal processing. More particularly, the present invention relates to multiple channel speech and audio signal processing.
2. Related Art
In a conventional voice-over-packet (“VoP”) system or voice over IP (“VoIP”) system, telephone conversations or analog voice may be transported over the local loop or the public switched telephone network (“PSTN”) to the central office (“CO”), where speech is digitized according to an existing protocol, such as G.711. From the CO, the digitized speech is transported to a gateway device at the edge of the packet-based network. The gateway device receives the digital speech and packetizes it. The gateway device can combine G.711 samples into a packet, or use any other compressing scheme. Next, the packetized data is transmitted over the packet network, such as the Internet, for reception by a remote gateway device and conversion back to analog voice in the reverse manner as described above.
For purposes of this application, the terms “speech coder” or “speech processor” will generally be used to describe the operation of a device that is capable of encoding speech for transmission over a packet-based network and/or decoding encoded speech received over the packet-based network. As noted above, the speech coder or speech processor may be implemented in a gateway device for conversion of speech samples into a packetized form that can be transmitted over a packet network and/or conversion of the packetized speech into speech samples.
A speech processor can be configured to handle the speech coding of multiple channels. Thus, input speech signal frames from multiple channels can be processed by the speech processor. With variable-rate codecs (coder-decoder), input speech signal frames are typically processed by adapting the bit-rate to the amount of information carried by the input speech signal frame, and may include a single-rate codec that uses discontinuous transmission (“DTX”). This variable bit-rate is associated with a variable processing complexity or coding algorithm complexity. In general, different bit-rates vary in complexity. Increased complexity corresponds to increased processing requirements. Conventional speech processors, however, inefficiently allocate its processing power. For example, in order to safeguard against exceeding their available computation power, conventional speech processors support a maximum channel density according to a worst-case definition, e.g., by assuming that the input speech signal frame for each channel will be processed with the highest complexity. As a consequence of this inefficient allocation of processing power, the price per port of such speech processors are significantly increased, which is undesirable.
Accordingly, there is a strong need in the art for a signal processing apparatus and method which provides efficient allocation of speech processing power.